Durnig the last two weeks my 4.6l (52000 miles) has developed a miss around 1300-1400 RPM when the transmission is in overdrive. I know this is lugging a bit but that's what you get @ 45 MPH.
I have searched many of the articles on this site and had some concerns about the Transmission. (Fluid and filter have been changed twice with the most recent a complete change including the torque converter and lines).
Today I ran the engine in different gears and noticed a definte miss under a load at various RPM between 1500-4000. The plugs and wires have approximately 5k on them.
I guess I will start with removing my chip, followed by new plugs????

Suggestions..............Thanks in advance

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F-150 extended cab, 4.6L, K&N Gen II, Gibson Cat-back single 3" exhaust, 8mm wires, Super Chip.

 

I've been dealing with that too. Dealer diagnosed it as #7 plug. $232 to change 1 plug.
I changed my plugs, went back to Sunoco Super, changed the Fuel Filter, and cleared the computer. This took care of the miss.
Check your vacuum lines. Especially that little one that goes from the FIPK to the drivers side valve cover. I put clamps on every hose to and from the FIPK, it cleared up a little of my rough idle.
I went in process of elimination and took out the chip and the FIPK to still see if it was missing with the stock setup. It was, but it's woth a try and it only costs you some time.

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97 F-150 4.6 4x4
K&N Fipk
Dual Flowmaster 50
Superchip
32" BFG's
Toyota stuck to bumper

 

Your post scared me! I ran out to my beloved truck and opened the hood quickly. Luckily, my 4.6 was still there.

Har Har

O.K., it wasn't that funny. I admit it.

 

ballistic,

Check the plug wires if you have a 97-98 and make sure the plug boots are on tight. Often times the ones near the firewall, hardest to install, are not seated properly.
because of this they ark in the plug well.
While you are about it check that the plugs are tight too.

Regards

Jean Marc Chartier

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00 F-150 XLT SC Flairside 4x4 4.6 w/5spd 3.55LSD
Warn XD9000i, skid plates, Draw tite class III,
Rancho RSX Reflex shocks, MAC 8.8 Axle Girdle
BFG 285/75 R16 MTs,
Borla Cat Back, Headman Headers,
Custom air intake system with modified
air box, Ported Throttle body,
Shortened MAF sensor tower,
K&N air filter,
Superchips

 

Ballistic!!!! I know the feeling. At 58000 miles my 4.6L was doing the same thing. I had it tuned up and it helped for a while. Three additionals sets of plug wires later it was still the same thing...a miss as soon as the transmission would shift into overdrive. My truck is currently in the shop (two weeks now) and they think they have found the problem. The tensioner pulley on the timing belt broke. Bent the valves in cylinder #1. Pulled heads and found valve giudes destroyed...I am unsure if this is the problem for the missing I experienced, but these things are certainly a problem. Will keep you advised...DaWG 03-16-2001.

 

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An update on DawG of Indpls' truck.

As stated in my previous message, the tensioner on the timing chain broke. I had been driving this vehicle with the same symptoms as "Ballistic" since 04-22-2000. The first Ford dealership that I did business with misdiagnosed it. They kept telling me it was the plug wires. They would replace the plug wires and it would run fine for a few days or weeks.
Finally, I got to another dealership that diagnosed the current problem. They diagnosed it by doing a bore scope on cylinder #1, and found a bend valve. After dismantling the motor, they found the bad tensioner and timing chain guide.
After three weeks, I was supposed to pick up my truck last evening (03-19-2001). The technician working on my truck started my truck for a test and the engine jumped time again. The fear is that there may be bent valves again. The heads are back off the motor.
So to make a long story short. Ballistic, save yourself a lot of frustration and have the timing checked on your vehicle, or have is bore scoped for a bent valve.
My current charges for this repair (and its not done yet) are $2000.00 USD. Besides that I have not had my truck for 3 weeks, and probably won't for at least a couple more days.

Good Luck.

DaWG of Indpls.